Well, it actually seems to hold true.
This isn't a bug, it's a _well-designed door_, not just your average hole that results from a bug.
It was probably carefully correct code, but what said code was doing was... evil.

Even then, generally when a closed project is opened, a _huge_ number of bugs are discovered and fixed.

Even through it will never be none, less is still less.

There are more security bugs reported for Linux than Windows/OS X, but they're generally minor, and are generally fixed more quickly.